[Pw_forum] convergence problem of FePc molecule

[Ari P Seitsonen]

Dear Kun Tao,

   My quick comments:

  - I would start learning Quantum ESPRESSO with _small_ molecules, not 
such big, slooooooooow ones; one can then start increase complexity little 
by little: DFT+U, isolated system, spin, ... all at the beginning is 
really tough

  - I would definitely not start learning QE with DFT+U scheme

  - Indeed the cut-off might a bit low

  - You try to magnetise the carbon atoms by 100 % (and none at iron); 
please check the documentation on the keyword 'starting_magnetization'

  - What are these '&' symbols on some lines? Do you want to comment them 
out?

     Greetings from ENS/Montrouge,

        apsi

-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-
   Ari Paavo Seitsonen / Ari.P.Seitsonen at iki.fi / http://www.iki.fi/~apsi/
   Ecole Normale Supérieure (ENS), Département de Chimie, Paris
   Mobile (F) : +33 789 37 24 25    (CH) : +41 79 71 90 935


On Mon, 1 Sep 2014, 琨陶 wrote:

> Dear all,
> 
> I just start to learn Quantum Espresso, and want to optimize the geometry of
> an FePc molecule. But, it doesn't converge even after 500 steps. Could you
> give me some suggestions? Any suggestions are welcome!
> 
> Regards,
> Kun Tao
> 
> 
> Attached below is the input file:
> 
> &CONTROL
>     calculation = 'scf'
>     restart_mode='from_scratch',
>     prefix='FePc',
>     pseudo_dir = './',
>     outdir='./temp'
>     etot_conv_thr=1.D-4
>     forc_conv_thr=1.D-2
>  /
>  &SYSTEM
>    ibrav=6,
>    celldm(1)=41.58,
>    celldm(3)=0.454545,
>    nat=  57,
>    ntyp= 4,
>    ecutwfc = 27.0,
>    ecutrho = 250.0,
>   & occupations='fixed',
>    smearing='marzari-vanderbilt',
>    degauss=0.1,
>    nspin=2,
>    assume_isolated = 'martyna-tuckerman'
>    starting_magnetization(1)= 1,
>   & lda_plus_u = .true.
>   & Hubbard_U(1)= 1.d-20
>   & Hubbard_U(2)= 1.d-20
>   & nbnd = 380
>  /
>  &ELECTRONS
>    diagonalization='cg',
>    conv_thr    = 1.D-4,
>    mixing_beta = 0.05D0,
>    electron_maxstep = 500,
>  /
> &IONS
>   & ion_dynamics = 'bfgs'
>    bfgs_ndim = 3
> /
> ATOMIC_SPECIES
>   C  12.0  C.pw91-van_ak.UPF
>   H  1.0  H.pw91-van_ak.UPF
>   N  14.0  N.pw91-van_ak.UPF
>   Fe 55.8  Fe.pw91-sp-van_ak.UPF
> ATOMIC_POSITIONS {Angstrom}
>  C   12.15539372    13.73909330    5.04996061
>  C   13.73649156    12.16178989    5.05578041
>  C   13.43098617    14.43384445    5.05163491
>  C   14.42783630    13.43936718    5.06136000
>  C   13.76218534    15.79065418    5.04836023
>  C   15.78316009    13.77488291    5.07699788
>  C   13.73909330    9.84460628    5.04996061
>  C   12.16178989    8.26350933    5.05578041
>  C   14.43384445    8.56901383    5.05163491
>  C   13.43936718    7.57216460    5.06136000
>  C   15.79065418    8.23781467    5.04836023
>  C   13.77488291    6.21683902    5.07699788
>  C   9.84460628    8.26090580    5.04996061
>  C   8.26350933    9.83821011    5.05578041
>  C   8.56901383    7.56615555    5.05163491
>  C   7.57216460    8.56063193    5.06136000
>  C   8.23781467    6.20934671    5.04836023
>  C   6.21683902    8.22511798    5.07699788
>  C   8.26090580    12.15539372    5.04996061
>  C   9.83821011    13.73649156    5.05578041
>  C   7.56615555    13.43098617    5.05163491
>  C   8.56063193    14.42783630    5.06136000
>  C   6.20934671    13.76218534    5.04836023
>  C   8.22511798    15.78316009    5.07699788
>  C   6.87043524    16.11305392    5.07808685
>  C   5.87526149    15.11545813    5.06072640
>  C   5.88694608    6.87043524    5.07808685
>  C   6.88454098    5.87526149    5.06072640
>  C   15.11545813    16.12473762    5.06072640
>  C   16.11305392    15.12956476    5.07808685
>  C   16.12473762    6.88454098    5.06072640
>  C   15.12956476    5.88694608    5.07808685
>  H   12.98551416    16.55329919    5.03687501
>  H   16.54878414    13.00105667    5.08993745
>  H   16.55329919    9.01448494    5.03687501
>  H   13.00105667    5.45121586    5.08993745
>  H   9.01448494    5.44669992    5.03687501
>  H   5.45121586    8.99894244    5.08993745
>  H   5.44669992    12.98551416    5.03687501
>  H   8.99894244    16.54878414    5.08993745
>  H   6.57077259    17.16044581    5.09259462
>  H   4.82672697    15.41213369    5.05869567
>  H   4.83955419    6.57077259    5.09259462
>  H   6.58786541    4.82672697    5.05869567
>  H   15.41213369    17.17327213    5.05869567
>  H   17.16044581    15.42922831    5.09259462
>  H   17.17327213    6.58786541    5.05869567
>  H   15.42922831    4.83955419    5.09259462
>  N   12.36901915    9.63413960    5.05092382
>  N   9.63413960    9.63097996    5.05092382
>  N   9.63097996    12.36585951    5.05092382
>  N   14.37677419    11.00406444    5.05336285
>  N   11.00406444    7.62322491    5.05336285
>  N   7.62322491    10.99593645    5.05336285
>  N   10.99593645    14.37677419    5.05336285
>  N   12.36585951    12.36901915    5.05092382
>  Fe   11.00000000    11.00000000    5.04961908
> K_POINTS Gamma
> 
>